Hi Tom,
Lets start troubleshooting with Teams settings page. In your Teams desktop app, click on User picture (upper right corner)> Settings> Devices. Check if the same device is set under Speakers and Microphone.
For the next step, please check if the issue persists in Teams Online.
Also, my suggestion would be to reinstall the drivers and re-add device to Teams.
If the issue persists, please try to repair your Office - Control panel> Programs> Programs and features> select Office 365> Change> Repair> Quick repair.
Does your organization have Skype for Business on prem server? Are you On prem, Hybrid or Pure cloud?
For the further troubleshooting, please provide me with all information.
Best regards,
Nemanja